Flashcards in Endocrine System Test Deck (27):
what does the endocrine system consist of ?
secreting cells in organs
diffuse from interstitial fluid to bloodstream & eventually to other cells called TARGET CELLS
Characteristics of endocrine system
what do hormones affect? what do they contain? receptors?
hormones affect target cells that respond to a specific hormone
-contain SPECIFIC RECEPTORS (proteins or glyoproteins)
-'site specific' (only accept 1 type of hormone)
Hormone types (2)
non-steroid includes what?
amines, peptides, proteins, glycoproteins
steroid hormones, thyroid hormones, nitric oxide (NO)
lipid-soluble (steroid) hormones
insoluble in water- but soluble in other lipids (EASY to enter cell membrane)
all derived from cholesterol
takes longer to act, but generally effects last longer than non-steroid hormones
-EX) puberty takes longer to act but lasts longer
action of steroid hormones
hormones transported in blood by transport proteins
diffuse through cell membrane (lipid bilayer) & bind to receptors within target cells
water soluble (non-steroid) hormones
composed of amine acids
cant diffuse through lipid-bilayer
bind to receptors on target cell surface
act faster, but effects are more short-lived than steroid hormones
EX) scared, heart rate increase (fight or flight)
Steroid hormone action (how steroid hormones work)
1) lipid soluble steroid hormone enters the target cell directly through cell membrane and binds to specific receptor (activation).
2) Activated hormone-receptor complex binds to specific genes of target cell's DNA & causes these genes to be expressed.
3) mRNA from hormone-activated genes leaves nucleus & starts to make new proteins
4) new proteins alter cell's activity in some specific way
Non-steroid hormone action (how non-steroid hormones work)
1) Water-soluble non-steroid hormone = first chemical message. Binds to specific receptor ON cell membrane of target cell (activation)
2) Hormone receptor complex stimulates formation of a SECOND messenger inside cell (cAMP). cAMP made from ATP by enzyme adenylate cyclase.
3) cAMP activates protein kinase enzymes -> activate other proteins by phosphorylation (adding phosphate)
4) many phosphorylated proteins alter cell's activity to elicit physiological responses
5) cAMP only lasts for short time before degraded
non-steroid vs steroid hormones
steroid: enters cell membrane, insoluble in water (transport proteins, receptors in target cell)
derived from cholesterol
long to act, effects last long
non-steroid: can't diffuse through lipid-bilayer (already has proteins, receptor on membrane)
composed of amino acids
act fast, short effects
Affect of aging on what 5 glands?
affects of aging on thymus gland
thymus gland shrinks significantly causing decreased immune cell production & decreased resistance to disease
affects of aging on pituitary gland
hGH secretion decreases, leading to muscle atrophy and weakness
affects of aging on kidneys
calcitriol secretion diminishes
affects of aging on pineal gland
secretion of melatonin is reduced w/ age, disrupts normal sleep-wake cycles
affects of aging on pancreas
insulin secretion and sensitivity of target tissue diminishes, affects changes in blood glucose ; increases = faster & return to normal glucose levels = more slowly
3 ways /methods hormones are controlled by the body
1. signals from NERVOUS SYSTEM
2. Chemical changes in BLOOD
3. act on OTHER HORMONES
Describe how hormones are controlled by the signals from the nervous system
nervous system -> endocrine gland -> target cells-> action
Describe how hormones are controlled by the chemical changes in the blood
blood -> endocrine gland -> target cells -> action
Describe how hormones are controlled by other hormones acting on each other?
hypothalamus -> ant. pituitary -> peripheral endocrine gland-> target cells -> action
how are hormonal secretions controlled in general?
controlled using negative feedback
1. Secretion triggered by internal/external stimulus
2. Rising hormone levels inhibit further hormone release in target organ
negative feedback of insulin
blood sugar level is high -> insulin is secreted, the change in blood glucose levels is detected, hypothalamus stops stimulating insulin production
negative feedback of glucagon
blood sugar level is low -> glucagon is secreted, the increase in blood glucose levels is detected, hypothalamus stops stimulating glucagon production
where is insulin and glucagon made? effect on body?
made in- pancreas
insulin-secreted by beta cells in pancreas, lowers blood glucose
glucagon- secreted by alpha cells in pancreas, raises blood glucose